User manual

FAQ for CBECC-Res 2013
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7. When modeling a mini-split heat pump, the compliance results are not as expected. Am I doing
something wrong?
No, you are probably not doing anything wrong. The field performance of these systems has not
been verified to justify the sometimes significantly more efficient SEER and HSPF ratings they are
given by the appliance standards test methods. Therefore, as explained in the ACM Reference
Manual, until there is a compliance option analysis of the efficiency of mini-split heat pumps, they
are modeled as equivalent to a ducted split system central heat pump.
8. What is the correct way to model a duplex or townhome? Can I call this a multi-family building?
While in the past it was possible to model the building as a single-family attached or multi-family,
because the duct leakage requirements are different for multi-family, these unique multi-family
projects must show compliance based on each dwelling unit. To obtain the correct results, each
dwelling unit will be modeled to produce its own CF1R.
9. Has any progress been made in speeding up the software?
Our programming team has reduced the run time by 50% on average by launching single-threaded
processes in parallel. Dual and quad-core processors are a critical part in seeing improvement, while
a single-core processor is not likely to show much improvement.
The greatest improvement is in all orientation compliance because all simulations are performed at
once. A rundown on the processing times for the sample files (results vary depending on the
complexity of the input file) are:
1StoryExample##.ribd 2:50 -->> 0:51
1StoryExample##Crawl.ribd 1:37 -->> 1:03
2Story2ZoneExample##.ribd 2:04 -->> 1:12
2StoryExample##.ribd 1:27 -->> 0:54
EAAExample##.ribd 2:05 -->> 1:13
AAExample##.ribd 0:57 -->> 0:35
MFexample##.ribd 1:25 -->> 0:45
10. Does the software allow a PC’s video card handle tasks that are separate from execution?
Staff has received a recommendation to compile the program to allow a PC's video card processor to
handle tasks that can be separated out for execution. There are three limitations:
• Single-threaded processes. The underlying program (CBECC/CSE) is not multi-threaded, so
there is no advantage to the video card processor mechanism without fairly substantial
changes to CSE and/or rules processor source.
• Compatibility. The solution we have implemented should work on any Windows OS system,
but video card solutions are hardware-specific, so some computers with certain video cards
would show an improvement while others would not.
• Cost. Although not ruled out completely, the cost/payout ratio is too high right now.
11. Does the software run on a Mac computer?
Some virtual machine applications such as BootCamp and Parallels enable the software to run on a
Mac computer and generate reports successfully.